Cancer metastasis is the primary cause of high mortality in breast cancer patients.In this study,we loaded an anti-cancer drug,cabazitaxel (CTX),into polymeric micelles (CTX-loaded polymeric micelles,PCMs),and explored their therapeutic efficacy in breast cancer metastasis.The characteristics of PCMs were investigated,and their anti-metastatic efficacy was assessed using in vitro and in vivo evaluations.PCMs had an average diameter of 50.13±11.96 nm with a CTX encapsulation efficiency of 97.02％±0.97％.PCMs could be effectively intealized into metastatic 4T1 breast cancer cells in vitro.CTX (10 ng/mL) or an equivalent concentration in PCMs did not significantly affected the viability of 4T1 cells,but dramatically decreased the cell migration activities.In an orthotopic metastatic breast cancer model,intravenously administered PCMs could be efficiently delivered to the tumor sites,resulting in a 71.6％ inhibition of tumor growth and a 93.5％ reduction of lung metastases.Taken together,our results verify the anti-metastatic efficacy of PCMs,thus providing an encouraging strategy for treating breast cancer metastasis.